<span>The eight major phyla of invertebrates are Porifera, Cnidaria, Platyhelminthes, Annelida, Most animals are invertebrates, and most of those are arthropods.</span><span>
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For the first blank it would be: Lock
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For the second blank it would be: Key
In certain organisms, like humans, there are two morphologically distinct types of gametes: (1) the male gamete (i.e. sperm cell) and (2) the female gamete (i.e. ovum). The male gamete is smaller in size and motile whereas the female gamete is several times bigger and non-motile. The haploid condition of the two gametes is essential so that at fertilization during sexual reproduction the integrity of the chromosomal number is maintained throughout generations.
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